著者

藤原 広行

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.66, no.4, pp.67-71, 2014-03-25 (Released:2014-05-20)

参考文献数

20

---

There is a similarity between the distribution of prime numbers and the pattern of earthquake occurrence. Earthquakes occur in a discrete manner in time and space. When viewed as a whole, however, we find some laws, such as Gutenberg-Richter law, that govern the entire earthquakes that seem to be individually independent. A similar phenomenon can be observed also in the world of number. The most basic example is the distribution of the prime numbers in integers. We consider a correspondence between earthquakes and prime numbers. We parameterize occurrence time of earthquakes as the prime numbers and magnitude of earthquakes as the interval of prime numbers. Then we obtain a relationship similar to Gutenberg-Richter law. We call the model obtained by this correspondence as “arithmetic seismic activity model”. If we can parameterize earthquakes using prime numbers, knowledge that has been cultivated in the number theory can be used for understanding of earthquakes. The distribution of prime numbers is related to the distribution of zeros of Riemann zeta function. Researches are in progress to understand the zeros of the Riemann zeta function as an eigenvalue problem of quantum dynamical system. Earthquake may be modeled as a phenomenon corresponding to a change in the energy level of a quantum dynamical system associated with prime numbers.

著者

加藤 護

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.70, pp.153-160, 2017-09-10 (Released:2017-10-11)

参考文献数

36

---

An MJMA 6.7 (Mw 6.2) earthquake occurred in Northern Nagano, Japan, on November 22, 2014. While the damage in the city center of Nagano was relatively minor, 65 stone lanterns, among 182, standing in the precinct of the Zenkoji Temple, approximately 25 km from the epicenter, were toppled by the ground motion of this earthquake. Damage of the surrounding residential area was minor. Directions of the collapse were dominantly in the north-south. Strong motion seismograms recorded at nearby JMA Nagano Local Meteorological Observatory were rich in high frequency, especially in the NS component, which explains collapse of stone objects whose natural periods are few tenths of a second. Similar damage was documented in a historic earthquake in 1714, and recurrence of such damage implies that high frequency ground motions from large earthquakes in this epicentral area have been repeated threats to the Zenkoji Temple and Nagano City.

著者

山中 浩明 瀬尾 和大 佐間野 隆憲 翠川 三郎

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.39, no.4, pp.607-620, 1986-12-25 (Released:2010-03-11)

参考文献数

21

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The seismic refraction prospecting was carried out in the southwestern part of the Tokyo Metropolitan area, to clarify the deep underground structure down to uppermost layer of the Earth's crust. The explosions were denoted at Nagatsuta, Kurokawa, Okazu and Yumenoshima. The explosion at Nagatsuta was planned to make clear the existence of vertical discontinuity of the basement between Nagatsuta and Yumenoshima, which has been suggested from the observation of Yumenoshima explosion. The underground structure was revealed by the travel time analysis. The main features of the underground structure are as follows:1) The underground structure consists of 4 layers. The P wave velocities of these layers are 1.8 to 2.0, 2.9, 4.8 and 5.5km/s, respectively.2) The thickness of the third leyer is several kilometers in this area, however this layer doesn't exist in the central part of the Kanto plain.3) The first layer is thinner than the second one in contrast with the underground structure of Yumenoshima situated on the center of the Kanto plain.4) The vertical discontinuity of the basement was not confirmed from Nagatsuta explosion, because the refracted wave from the basement was not observed as an initial motion at the expected stations.

著者

田中館 秀三

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.10, no.12, pp.529-542, 1938-12-25 (Released:2010-03-09)

被引用文献数

1

著者

後藤 和彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.65, no.3, pp.231-242, 2013-01-31 (Released:2013-07-19)

参考文献数

28

被引用文献数

7 9

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The hypocenter of the 1911 great earthquake occurred around Kikai-jima, Japan is thought to be 28.0°N, 130.0°E (about 30km southward from Kikai-jima) and 100km depth in general. This implies that the 1911 event occurred within the subducting slab at the Ryukyu trench. However, it is not clearly known what kind of seismic data were used to determine the epicenter and how the depth of hypocenter was estimated quantitatively. In the present study, we determine hypocenter of this event by using selected S-P time data not only reported ones but also re-measured ones from smoked-paper seismograms. The hypocenter is revealed to be 28.7°N, 130.6°E and 60km in depth, about 60km northeastward from Kikai-jima. The focal depth is, however, considered to be about 10km instead of 60km by referring to the present hypocenter distribution because of the low reliability of focal depth in the relocation. Recent epicenter distribution shows the low seismic activity area on the plate boundary northeast off Kikai-jima which extends about 70km length parallel to the Ryukyu trench axis. The 1911 great earthquake seems to be occurred at the shallower rim of this low seismic activity area. If the low seismic activity is the result of strong coupling on plate boundary, this area might be the asperity of the 1911 great earthquake. Tsunami heights accompanied with this event are reported recently to be more than 5m at Kikai-jima and Amami-oshima, which supports the present study that the 1911 great earthquake is the interplate event rather than the intraslab one.

著者

武村 雅之 池浦 友則 工藤 一嘉 大沼 啓人

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.47, no.2, pp.193-200, 1994-08-14 (Released:2010-03-11)

参考文献数

15

被引用文献数

4

著者

加藤 護 岡本 義雄

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.69, pp.35-39, 2016-11-10 (Released:2017-01-07)

参考文献数

40

著者

佐々木 晶

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.61, no.Supplement, pp.285-296, 2009-07-31 (Released:2013-11-21)

参考文献数

46

---

The interior structures of planets and satellites have been investigated through various methods. Density is the most fundamental information for estimating the composition of solar system bodies. Moment of inertia expressing the mass concentration is a key for investigating the interior structure. It can be obtained from spacecraft flyby with a planet or a satellite. Interior density structure of a planet is evaluated from gravity field which is estimated from orbital tracking of spacecraft around the planet. KAGUYA first successfully obtained the accurate far-side gravity field of the Moon. Detailed interior structure can be estimated from seismic methods. Direct seismic measurements had been developed on the nearside of the Moon by the Apollo project. Seismograms of moonquakes, reflecting less interior dissipation, are different from those of the Earth. Radar sounders have been successful in measuring subsurface structure of the Moon and Mars. The state of the planetary interior, especially of the core, can be discussed using the measurement of variation of planetary rotation. The study of the planetary interior is now being extended into extrasolar planets.

著者

小林 芳正

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.32, no.1, pp.57-73, 1979-03-25 (Released:2010-03-11)

参考文献数

13

被引用文献数

2 2

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The Great Kanto earthquake, 1923, triggered a catastrophic debris flow which devastated the village of Nebukawa with a loss of 300 to 400 lives. The buried area at Nebukawa is determined by synthesizing eyewitness accounts, photographs, the character of surface soils, etc. The moment of rushing at Nebukawa is estimated at about 5 minutes after the mainshock onset from the eyewitness accounts and aftershock records. The temporal change in topography in the mountain region is investigated by comparing topography maps prior and after the earthquake, and a probable source of the debris flow is assumed at a large depressed area, Obora about 4km upstream Nebukawa. The grain-size distributions of the debris-flow deposits and those of mountain soils are also consistent with this assumption.

著者

大見 士朗 和田 博夫 濱田 勇輝

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.65, no.1, pp.85-94, 2012-09-28 (Released:2012-10-26)

参考文献数

15

被引用文献数

2 3

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Seismic activity near the Yake-dake (Mt. Yake) volcano in the Hida mountain range that took place immediate after the 2011 off the Pacific Coast of Tohoku earthquake was investigated. It initiated about ten minutes after the mainshock of the Tohoku earthquake and lasted for about one month. At the beginning, two active swarms were observed. One is at the northern flank of the Yake-dake volcano and the other is located between Yake-dake and Mt. Norikura volcanoes. The latter activity decreased by March 20, and the former activity lasted until early April. It includes two M≥4.5 earthquakes and we could locate more than 9,600 events in the study area during March and April. We mainly focused on the activity near the Yake-dake volcano in this paper. Near the Yake-dake volcano, seismic activity began with M4.7 (JMA) earthquake at 14:57 JST on March 11. This M4.7 event is located 3 km north to the volcano and seismicity increased between the summit of the Yake-dake volcano and the hypocenter. On March 21, an M4.8 (JMA) event took place at 13:15 JST also at 3 km north to the volcano. After this second M≥4.5 earthquake, seismic activity migrated to the north about 1 km. Focal mechanism solutions of these swarm earthquakes show NW-SE compression stress field, which coincides with regional stress field indicated by previous studies. No temporal changes of focal mechanisms are shown during March and April, which probably indicates no magmatic activity such as dyke intrusion related to the Yake-dake volcano took place in this time period.

著者

阿部 邦昭

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.49, no.1, pp.1-9, 1996-05-24 (Released:2010-03-11)

参考文献数

15

被引用文献数

2 2

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Local amplifications of tsunami were found on the maximum inundation heights at Japanese 10 coasts facing islands in the 1993 Hokkaido nansei-oki earthquake tsunami. For each island-coast geography a peak height (H) at a coastal focus, a background average height (H0), a peak width (Wd), a coastal focus distance from the island (L) and an island size (L0) are defined on the space distribution of maximum heights obtained in the surveys and the relations are discussed.Main results are as follows: Amplification ratio H/H0, plotted as a function of coastal focus distance from an island, are distributed in the vicinity of 2. The peak width relative to the island size Wd/L0 is proportional to the focus distance relative to the island size L/L0. There is a negative correlation relation between the amplification ratio and the relative peak width. These facts suggest that the amplification was caused by a superposition of incident waves on the sea in the rear of the island slope after being separated into two and refracted on the slope. Thus, the amplification at the coast facing islands is explained from a focusing effect of islands on a tsunami.

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.5, no.9, pp.585-595, 1933-09-15 (Released:2010-11-17)

著者

岩田 貴樹

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.61, no.Supplement, pp.133-141, 2009-07-31 (Released:2013-11-21)

参考文献数

70

被引用文献数

3

---

In recent years, many researchers in seismicity analysis have focused on earthquake triggering or fault interactions.To evaluate these phenomena quantitatively, models for the spatio-temporal distribution of seismic activity have been constructed. This review paper introduces two important models : the ETAS (epidemic-type aftershock sequence) model developed by Y. Ogata and a seismicity model based on rate- and state-dependent friction law by J. Dieterich. The former is a pure statistical model, while the latter includes some physical parameters in its derivation.These two models now play separate role in probabilistic earthquake forecasting. For further achievement in the probabilistic earthquake forecasting, the integration of the two contrasting models should be considered. Further development of models would give new insights into earthquake occurrence.

著者

田村 慎 笠原 稔 森谷 武男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.55, no.4, pp.337-350, 2003-03-15 (Released:2010-03-09)

参考文献数

27

被引用文献数

4 4

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We have studied micro-seismicity in the northern part of Hokkaido (north above 44°N) from June to November in 1998 combining eleven temporal seismic stations with seven and five routine ones operated by Institute of Seismology and Volcanology (ISV) in Hokkaido University and Sapporo Meteorological Observatory, Japan Meteorological Agency (SMO), respectively.Firstly we determined 91 hypocenters of local earthquakes in this period using the dense network. These hypocenters are about three times of the number of those from the routine network alone. One-dimensional P-wave velocity structure assuming four-layer model (assumed thickness of 2, 8, 10km and infinite) and station corrections were estimated using a P-wave travel time inversion method with 735 P-wave arrival time records of 81 events. The velocity of each layer was determined to be 2.83km/sec for the first layer, 5.32km/sec for the second one, 6.32km/sec for the third one and 6.69km/sec for the bottom half space. From the P-wave station corrections we obtained, this region can be classified into three zones parallel in the north-south direction; the western islands region in the Sea of Japan, the western part of mainland, and the eastern part of mainland. Each zone shows the value of less than-0.5sec, +0.1-+0.4sec, and-0.1--0.5sec, respectively.Next, the hypocenters with the inverted velocity structure and the station corrections are relocated. As the results show, some hypocenters in the anomalous delayed station correction zone, i. e. the western part of mainland, are clearly located at the depth range from 20 to 25 km. Focal mechanism solutions of these deep events show normal fault type, while shallower events less than 20 km depth show strike-slip and reverse fault types. We also relocated 381 earthquake hypocenters which were routinely determined by ISV from October 1996 to December 2000. According to the relocated hypocenter distribution, a high seismic zone is shown in the western part of mainland with about 50km wide along a north-south direction. On the other hand, the eastern part of mainland is strongly characterized as aseismic zone. The boundary between the seismic and aseismic zones corresponds to the geological boundary between Kamuikotan metamorphic belt and Hidaka belt.

著者

束田 進也 小高 俊一 芦谷 公稔 大竹 和生 野坂 大輔

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.56, no.4, pp.351-361, 2004-03-25 (Released:2010-03-11)

参考文献数

18

被引用文献数

11 27

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We have found that the envelope waveform of the initial part of P waves changes systematically with magnitude and epicentral distance. In order to represent the envelope waveform quantitatively we introduced a simple function of the form of Bt·exp(-At). Two parameters A and B can easily be determined by the least-squares method. The parameter B defines the slope of the initial part of the P-wave envelope and A is related to the amplitude growth or decay with time. When A is positive, B/(Ae) gives the maximum amplitude where e denotes the base of natural logarithm. This case is typical for small earthquakes, indicating that the initial amplitude increases sharply and decays quickly soon after the P-wave arrival. When A is negative, the amplitude increases exponentially with time. This is a characteristic of large earthquakes.We have found from the analysis of actual seismic data that log B is inversely proportional to the epicentral distance Δ even though the dispersion of data is somewhat large. This relation seems to be independent of earthquake magnitude and thus, by using this relation, we can roughly estimate the epicentral distance immediately after the P-wave arrival. Then, we can estimate the magnitude easily from the formula, similar to the conventional magnitude-amplitude relation, M=α·logVmax+β·logB+γ, where Vmax is the P-wave maximum amplitude within a given short time interval (e. g., 3 seconds) after the P-wave arrival. For M7- and M8-class earthquakes whose rupture duration reaches 10 sec or more, we need to estimate the magnitude repeatedly with time as the amplitude increases.The decrease of the parameter B with distance may be caused by anelasticity of the medium, scattering and geometrical spreading of P waves during propagation.

著者

鎌谷 紀子 勝間田 明男

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.57, no.1, pp.11-28, 2004-08-25 (Released:2010-03-11)

参考文献数

30

被引用文献数

5

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In recent years, improved seismic networks in Japan have detected low-frequency events near the Mohorovicic discontinuity, but away from volcanoes. These can be classified as two types: low-frequency earthquakes (LFE) and low-frequency tremors (LFT). Source regions for LFE are distributed in isolated locations throughout Japan, while those for LFT are distributed within a belt in western Japan. Although LFE immediately below volcanoes have been previously recognized, LFE away from volcanoes represent new observations. These LFE are found specifically both in the back-arc of the volcanic front in northeastern Japan, and to the north of the LFT belt in western Japan. LFE and LFT have long durations, suggesting the involvement of fluids in their generation. This study considers the source processes that trigger LFE and LFT, using the results of high pressure and temperature experiments on water-saturated oceanic basalt and peridotite as a model. Such materials are representative of those in and around the descending slab. In the case of LFT in western Japan, the model provides, as a possible trigger, the water released by the dehydration of chlorite and forming clinopyroxene in the basalt of the descending Philippine Sea Plate. On the other hand, in the case of LFE throughout Japan, not only water from the slab but also magma generated in the slab and mantle wedge and high temperature fluid derived from the magma are possible triggers. Because LFE have clear P-wave onsets, some sort of fracture is likely to be involved in the generation of LFE. LFE and LFT are expected to be indicators useful in earthquake prediction, but the relationships between large earthquakes or earthquake swarms and the occurrence of LFE and LFT are yet to be determined.

著者

今村 明恒

出版者

公益社団法人 日本地震学会

雑誌

地震 第1輯 (ISSN:00371114)

巻号頁・発行日

vol.15, no.6, pp.150-155, 1943-06-18 (Released:2010-11-17)

著者

浜口 博之 後藤 和彦

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.34, no.1, pp.145-147, 1981-03-25 (Released:2010-03-11)

参考文献数

10

被引用文献数

1

著者

鷺谷 威

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.56, no.2, pp.199-211, 2003-09-16 (Released:2010-03-11)

参考文献数

22

被引用文献数

1

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The 1918 Omachi Earthquake occurred near Omachi city, along the northern Itoigawa-Shizuoka Tectonic Line Fault Zone. Leveling data associated with the earthquake were re-examined and corrected for artificial alteration. Corrected leveling data revealed about 200mm of uplift in the central Omachi and a slight subsidence in the southern part. However, the leveling data are not enough to resolve a fault model of the Omachi earthquake by themselves. Therefore a new fault model is developed based on the leveling, triangulation, and structural data. Estimated fault plane is 4.4km×10.0km wide, shallowly inclined to ENE at the base of the Matsumoto Basin. Estimated fault slip amounts to 1.2m and the seismic moment is estimated to be 1.8×1018Nm (Mw=6.1). The fault model is consistent with the observed surface rupture and horizontal crustal strain, which have been hardly explained by previous models. The 1918 Omachi earthquake is considered to have released WNW-ESE compressional stress by rupturing a shallow part of the crust. Although the source fault is discriminated from the East Matsumoto Basin Fault, these faults are interpreted to be the members of the same fault system. An integrated understanding of the whole fault system as well as inelastic deformation in the surrounding area is necessary to refine estimates on earthquake probabilities and strong ground motions.

著者

織原 義明 鴨川 仁 野田 洋一

出版者

公益社団法人 日本地震学会

雑誌

地震 第2輯 (ISSN:00371114)

巻号頁・発行日

vol.67, no.2, pp.81-85, 2014-09-30 (Released:2014-11-25)

参考文献数

14

被引用文献数

2 2